13.2 Quality Control, Material Test Reports (MTRs), Weld Mapping & Traceability

12.2 Quality Control, Material Test Reports (MTRs), Weld Mapping & Traceability

Core Trade Concept: Quality Control (QC) in boilermaking is the systematic process of ensuring that every piece of plate, pipe, forging, filler metal, and welded joint meets rigid engineering and Code specifications. A failure in material identification or welding documentation can result in catastrophic in-service ruptures. Boilermakers must understand Quality Control Systems, Certified Mill Test Reports (CMTRs), low-stress material marking, weld mapping, and Non-Conformance Reporting (NCR).

1. Quality Control System & Traveler Sheets

An ASME Certificate Holder must establish and maintain a documented Quality Control (QC) Manual that outlines organizational responsibilities, fabrication procedures, and examination protocols.

                      QC SYSTEM ORGANIZATIONAL HIERARCHY
                      
                         +-----------------------+
                         |   Company Executive   |
                         |       Management      |
                         +-----------------------+
                                     |
                  +------------------+------------------+
                  |                                     |
                  v                                     v
       +---------------------+               +---------------------+
       |  Production / Shop  |               |   Quality Control   |
       |     Supervision     |               |      Manager        |
       +---------------------+               +---------------------+
                  |                                     |
                  |                                     v
                  |                          +---------------------+
                  |                          |  QC Inspectors /    |
                  |                          |  NDE Examiners      |
                  |                          +---------------------+
                  |                                     |
                  +==================+==================+
                                     |
                                     v
                         +-----------------------+
                         | Authorized Inspector  |
                         |      (AI / AIA)       |
                         +-----------------------+

Key Principles of the QC System

1. Organizational Independence: The Quality Control department must operate with authority independent of production pressures. QC inspectors must have the direct authority to stop work, reject non-conforming materials, and enforce hold points.
2. Travelers / Process Router Sheets: The traveler (or route sheet) is the master tracking document that travels with a component through each stage of fabrication, welding, inspection, and testing.

                         TYPICAL FABRICATION TRAVELER ENTRY
                         
   +-----+-------------------------------+-------------+----------+-----------+
   | Op  | Operation Description         | QC Sign/Date| AI Sign  | Hold/Wit. |
   +-----+-------------------------------+-------------+----------+-----------+
   | 10  | Material Verification & CMTR  | JS 08/12/26 | --       | Review    |
   | 20  | Cut & Bevel Shell Plates      | JS 08/13/26 | --       | QC Point  |
   | 30  | Fit-up & Root Gap Inspection  | JS 08/14/26 | --       | QC Point  |
   | 40  | Long. Seam Root Pass Weld     | JS 08/14/26 | --       | In-Process|
   | 50  | 100% Radiographic Examination | TR 08/16/26 | AI 08/17 | Review    |
   | 60  | Post-Weld Heat Treat (PWHT)   | JS 08/18/26 | AI 08/19 | Hold Point|
   | 70  | Final Hydrostatic Test (900#) | JS 08/20/26 | AI 08/20 | HOLD POINT|
   +-----+-------------------------------+-------------+----------+-----------+

Inspection Checkpoint Classifications

• Hold Point: A critical mandatory milestone on the traveler. Fabrication CANNOT proceed past a Hold Point until the designated QC inspector or Authorized Inspector has physically inspected the work, verified compliance, and signed/dated the traveler.
• Witness Point: A scheduled inspection milestone where the AI or owner's inspector is notified in advance. If the inspector is not present at the appointed time, fabrication may proceed only if prior written agreement exists.
• Review Point: A documentary checkpoint where the inspector reviews examination records, radiographic films, heat treatment charts, or CMTRs prior to final equipment release.

2. Certified Mill Test Reports (CMTRs) & Metallurgical Properties

A Certified Material Test Report (CMTR), or Mill Test Report (MTR), is a certified legal document issued by the steel mill verifying that a specific batch of metal meets all chemical and mechanical requirements of the referenced ASME Section II material specification.

                      CERTIFIED MILL TEST REPORT BREAKDOWN
                      
 +-----------------------------------------------------------------------------+
 | TITAN STEEL MILLS CORP.                     CERTIFIED MATERIAL TEST REPORT  |
 | Material: ASME SA-516 Grade 70 (PVQ Plate)  Heat Number: H-847291           |
 | Dimensions: 1.500" x 96.0" x 240.0"         Slab Number: SL-4402            |
 +-----------------------------------------------------------------------------+
 | CHEMICAL COMPOSITION (Weight %)                                             |
 |   C     Mn     P      S      Si     Cr     Mo     Ni     V      CE (IIW)  |
 | 0.22  1.15  0.012  0.004   0.28   0.04   0.02   0.03   0.005    0.43%    |
 +-----------------------------------------------------------------------------+
 | MECHANICAL PROPERTIES                                                       |
 | Yield Strength (0.2% offset)   : 48,500 psi  (Spec Min: 38,000 psi)         |
 | Tensile Strength               : 76,200 psi  (Spec: 70,000 - 90,000 psi)    |
 | Elongation in 2"               : 27.0 %      (Spec Min: 21.0 %)             |
 | Charpy V-Notch (-20°F Avg)     : 34 ft-lbs   (Spec Min: 20 ft-lbs)          |
 +-----------------------------------------------------------------------------+

Critical Elements on an MTR

1. Material Specification & Grade: Must explicitly match the ASME Section II designation (e.g., SA-516 Gr 70, SA-335 Gr P91, SA-106 Gr B).
2. Heat Number: A unique tracking number assigned to a specific batch of molten steel in the mill's furnace ladle. Every plate or pipe rolled from that ladle shares this heat number.
3. Chemical Composition: Details weight percentages of alloying elements:
   • Carbon ($C$): Primary strengthening element; higher carbon increases hardness and tensile strength but reduces ductility and weldability.
   • Manganese ($Mn$): Increases strength and toughness; scavenges sulfur.
   • Phosphorus ($P$) & Sulfur ($S$): Harmful impurities that cause hot-shortness, lamellar tearing, and embrittlement. ASME specifications set strict maximum thresholds (e.g., $P \le 0.025%$, $S \le 0.015%$).
   • Chromium ($Cr$) & Molybdenum ($Mo$): Enhance high-temperature creep strength, oxidation resistance, and corrosion resistance.

Carbon Equivalent (CE) & Weldability

The Carbon Equivalent (CE) formula evaluates the combined hardenability of steel and its susceptibility to Hydrogen-Induced Cracking (HIC) in the Heat-Affected Zone (HAZ):

$CE = \%C + \frac{\%Mn + \%Si}{6} + \frac{\%Cr + \%Mo + \%V}{5} + \frac{\%Ni + \%Cu}{15}$

$\text{Engineering Rule: } CE > 0.40\% \text{ requires elevated preheat; } CE > 0.45\% \text{ requires strict preheat and low-hydrogen filler metals. }$

Mechanical Properties

• Yield Strength ($S_y$): The stress level at which the steel permanently deforms plastically.
• Tensile Strength ($S_u$): The maximum engineering stress the material can sustain before necking and fracture.
• Elongation (% in 2 inches): Measures ductility—the ability of the steel to deform plastically without tearing.
• Charpy V-Notch (CVN) Impact Energy: Measures notch toughness (absorbed energy in $\text{ft-lbs}$ or Joules) at a designated test temperature (e.g., $-20^\circ\text{F}$ or $-50^\circ\text{F}$). High CVN values confirm the steel will not suffer catastrophic brittle fracture under low operating temperatures or high impact shock.

3. Material Traceability & Physical Marking Requirements

Positive Material Identification (PMI) and complete heat number traceability must be maintained from raw warehouse stock through completed boiler commissioning.

                      HEAT NUMBER TRANSFER BEFORE CUTTING
                      
         Raw Steel Plate (Heat H-847291)          Cut Sections (Traceability Preserved)
       +-------------------------------+          +---------------+ +---------------+
       | [H-847291]                    |          | [H-847291]    | | [H-847291]    |
       | SA-516 Gr 70                  |  =====>  | SA-516 Gr 70  | | SA-516 Gr 70  |
       |                               | Cut Line | (Transferred) | | (Transferred) |
       +-------------------------------+          +---------------+ +---------------+

Heat Number Transfer Rules

Mandatory Code Rule: Before cutting, burning, or shearing any pressure vessel plate or pipe, the original mill heat number, specification, and grade must be transferred to all cutoff sections using an approved marking method. If traceability is lost, the material is deemed non-conforming and cannot be used in pressure boundary fabrication.

Approved Marking Techniques vs. Prohibited Sharp Stamps

                     APPROVED VS. PROHIBITED MARKING TOOLS
                     
       PROHIBITED ON PRESSURE BOUNDARY            APPROVED LOW-STRESS MARKING
            Sharp "V-Notch" Die Stamp               Dot-Matrix / Radiused Die Stamp
                 |     |                                   :     :
                 |     |                                   :     :
                 \     /                                   (     )
                  \ _ /                                     \ _ /
          (Creates Sharp Notch;                    (Blunt Spherical Indentation;
         Initiates Fatigue Cracks)                  Prevents Stress Risers)

1. Prohibited Sharp "V-Notch" Die Stamps: Conventional sharp-bottom steel stamps create deep, microscopic V-shaped notches in the metal surface. Under cyclic pressure loading and thermal fatigue, these notches act as severe stress concentrations (stress risers) that initiate rapid crack propagation.
2. Approved Low-Stress Stamping:
   • Low-Stress Dot-Matrix Stamps: Form characters from rounded micro-dots.
   • Round-Nose (Radiused) Die Stamps: Character edges have a minimum radius of $0.010\text{ in.}$ ($0.25\text{ mm}$) to produce smooth, spherical indentations without sharp root notches.
   • Vibro-Etching / Electrochemical Etching: High-frequency reciprocating carbide styluses or chemical etching that produce shallow, non-stress-concentrating markings.
   • Paint Stenciling: High-visibility, chloride-free, low-sulfur industrial paint markers (mandatory on austenitic stainless steels and high-nickel alloys).

4. Weld Mapping, Welder Identification & Filler Metal Control

Weld Mapping Architecture

A weld map is a detailed fabrication drawing or isometric schematic that assigns a unique, sequential identification number to every pressure boundary weld on a vessel or piping system.

                       BOILER DRUM WELD MAP SCHEMATIC
                       
                 W-01 (Circ Seam)                     W-03 (Circ Seam)
                   |                                    |
         +---------v-------+--------------------+-------v---------+
         |   HEAD 1        |    SHELL COURSE    |    HEAD 2       |
         |                 |                    |                 |
         |                 |    W-02 (Long Seam)|                 |
         |                 +====================+                 |
         +---------+-------+----------+---------+-------+---------+
                   |                  |                 |
                 W-04 (Nozzle)      W-05 (Manway)     W-06 (Nozzle)

The Weld Tracking Record (Weld Log)

Each weld number on the weld map links directly to a row in the master Weld Record Log:

Welder Identification Stenciling

• Under ASME Section I (PW-28) and Section VIII (UW-29), each certified welder is assigned a unique identifying number, letter, or symbol.
• Upon completing a joint, the welder must stamp or stencil their assigned ID within $1\text{ to }2\text{ inches}$ of the weld bead on the base plate using low-stress stamps.
• If physical stamping is prohibited (e.g., thin-wall titanium or stainless tubing), the weld map traveler serves as the legal record of welder identification.

Filler Metal Control Protocols

                     FILLER METAL STORAGE & ISSUE CYCLE
                     
       +--------------------+      +--------------------+      +--------------------+
       | Sealed Mill Cans   |      | Holding Oven       |      | Heated Quivers     |
       | Hermetically sealed| ===> | 250°F - 350°F      | ===> | 150°F - 250°F      |
       | dry warehouse      |      | Continuous bake    |      | 4-Hour Field Limit |
       +--------------------+      +--------------------+      +--------------------+

1. Low-Hydrogen SMAW Electrodes (E7018, E8018, E9018): Moisture absorption in electrode flux coatings releases atomic hydrogen into the molten weld puddle, causing delayed hydrogen underbead cracking. Electrodes must be stored in holding ovens maintained between $250^\circ\text{F}\text{ and }350^\circ\text{F}$ immediately after opening hermetically sealed cans.
2. 4-Hour Field Exposure Rule: Once issued to boilermakers in portable heated rod quivers, low-hydrogen electrodes must be consumed within 4 hours (or returned to holding/rebaking ovens per manufacturer instructions).

5. Non-Conformance Reports (NCR) & Dispositioning

A Non-Conformance Report (NCR) is a formal quality document used to record, evaluate, and correct any condition in material, fabrication, or documentation that fails to meet drawings, technical specifications, or ASME Code requirements.

                         NCR WORKFLOW & DISPOSITIONING
                         
         +-------------------------------------------------------------+
         | 1. IDENTIFICATION                                           |
         | Deviation detected (e.g., crack, mismatch, wrong filler).   |
         | NCR issued; red 'HOLD' tag applied; part quarantined.       |
         +-------------------------------------------------------------+
                                        |
                                        v
         +-------------------------------------------------------------+
         | 2. TECHNICAL EVALUATION & DISPOSITIONING                     |
         | QC, Engineering & AI evaluate severity and assign action:   |
         |                                                             |
         | • REWORK      : Bring into original drawing compliance.     |
         | • REPAIR      : Make acceptable using engineered procedure. |
         | • ACCEPT-AS-IS: Engineering calculation verifies safety.    |
         | • SCRAP       : Unsalvageable; destroy and discard.         |
         +-------------------------------------------------------------+
                                        |
                                        v
         +-------------------------------------------------------------+
         | 3. ROOT CAUSE CORRECTIVE ACTION (RCCA)                      |
         | Perform 5-Why analysis, retrain welders, close NCR.         |
         +-------------------------------------------------------------+

The Four Standard Dispositions

1. Rework: Making the non-conforming item conform to original drawing and specification requirements using standard manufacturing procedures (e.g., adding weld metal to an undersized fillet weld leg, or re-machining a flange face to correct surface finish).
2. Repair: Making the item acceptable for its intended purpose, even though the final repaired condition does not conform to original blueprints. Requires an engineered repair procedure and concurrence from the Authorized Inspector (e.g., gouging out a deep crack, buttering the cavity, and applying a qualified temper-bead weld procedure).
3. Accept-As-Is (Use-As-Is): Leaving the non-conforming condition uncorrected after engineering evaluation and stress calculations prove that design margins, MAWP, and Code criteria are fully satisfied (requires formal engineering review and AI approval).
4. Scrap: The non-conformance cannot be safely repaired or used. The item is painted with red scrap markers, physically removed from the fabrication line, and quarantined to prevent inadvertent installation.